The present invention relates to a channel allocation system for a distributed processing system, and more particularly, to a channel allocation system for routing voice and data transmissions in a distributed digital switching network.
Multi-line telephone key stations, sometimes referred to as "trader turrets", are widely used in rapid communication networks such as trading operations in banks, brokerage houses, and other financial institutions. Telephones of this type provide direct access to a large number of telephone lines with a line being selected by the depression of a single key on the key station. A large trading room can include many telephone key stations for simultaneously completing many transactions each involving millions of dollars. Trader turrets generally include at least thirty line keys and often have several hundred. Trader turrets are normally used in networks where the number of lines is greater than the number of telephones whereas, with normal telephone key stations, the number of telephones exceeds the number of lines.
Each telephone key station may have access to other telephone key stations in the system within a trading room and to a large number of outside lines and private lines. Each telephone user may be connected to several lines or terminals at the same time in a conferencing mode.
A typical trading transaction involves a rapid series of short telephone conversations to, for example, locate traders having the desired security for sale at the best price. A typical call lasts for a few seconds and there may be many calls per minute during the course of a single transaction. It is important for a trader to have immediate access to outside lines irrespective of system load conditions.
The financial trading environment places heavy performance demands on the switching network. The switching network must employ distributed control so that there can be no single point failure of the trading network. The switching network must be highly redundant so that alternate routes through the network are available by passing faults that may occur. The system must further be essentially non-blocking so that traders will never encounter a "busy" signal in the course of unimportant transactions. In a highly redundant, non-blocking, distributed, switching network, the switching elements are faced with efficiently making the best route selection from among a large number of choices. Failure to make such selections efficiently results in unacceptably slow switch operation. Failure to select the best available route results in inefficient use of the switch capacity.